package chapter05;

import java.util.Scanner;

public class PrintCalendar {

	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.println("Enter full year (e.g.,2001): ");
		int year = input.nextInt();
		
		System.out.println("Enter month in number between 1 and 12: ");
		int month = input.nextInt();
		printMonth(year, month);
		input.close();
	}
	
	public static void printMonth(int year, int month){
		printMonthTitle(year, month);
		printMonthBody(year, month);
	}
	
	public static void printMonthTitle(int year, int month){
		System.out.println("         " + getMonthName(month) + " " + year);
		System.out.println("-----------------------------");
		System.out.println(" Sun Mon Tue Wed Thu Fri Sat");
	}
	
	public static String getMonthName(int month){
		String monthName = "";
		switch (month){
			case 1:monthName = "January";break;
			case 2:monthName = "February";break;
			case 3:monthName = "March";break;
			case 4:monthName = "April";break;
			case 5:monthName = "May";break;
			case 6:monthName = "June";break;
			case 7:monthName = "July";break;
			case 8:monthName = "August";break;
			case 9:monthName = "September";break;
			case 10:monthName = "October";break;
			case 11:monthName = "November";break;
			case 12:monthName = "December";
		}
		return monthName;
	}
	
	public static void printMonthBody(int year, int month){
		int startDay = getStartDay(year, month);
		int numberOfDaysInMonth = getNumberOfDaysInMonth(year, month);
		
		int i = 0;
		for(i = 0; i < startDay; i++){
			System.out.print("    ");
		}
		
		for (i = 1; i <= numberOfDaysInMonth; i++){
			System.out.printf("%4d", i);
			if ((i + startDay) % 7 == 0){
				System.out.println();
			}
		}
		
		System.out.println();
	}

	public static int getStartDay(int year, int month){
		final int START_DAY_FOR_JAN_1_1800 = 3;
		int totalNumberOfDays = getTotalNumberOfDays(year, month);
		return (totalNumberOfDays + START_DAY_FOR_JAN_1_1800) % 7;
	}
	
	public static int getTotalNumberOfDays(int year, int month){
		int total = 0;
		for (int i = 1800; i < year; i++){
			if (isLeapYear(i))
				total += 366;
			else
				total += 365;
		}
		for (int i = 0; i < month; i++){
			total += getNumberOfDaysInMonth(year, i);
		}
		
		return total;
	}
	
	public static int getNumberOfDaysInMonth(int year, int month){
		int[] bigMonths = {1, 3, 5, 7, 8, 10, 12};
		int[] smallMonths = {4, 6, 9, 11};
		for (int i: bigMonths){
			if(month == i)
				return 31;
		}
		
		for (int i: smallMonths){
			if (month == i)
				return 30;
		}
		
		if (month == 2)
			return isLeapYear(year)? 29: 28;
		return 0;
	}
	
	public static boolean isLeapYear(int year){
		return (year % 100 != 0 && year % 4 == 0 || year % 400 == 0);
	}
}
